From late 14c. as "lightheartedness, cheerfulness." A word with more senses in Middle and early Modern English than recently: "sexual pleasure or indulgence, lust" (mid-14c.); "insolent presumptuousness, impudence" (mid-14c.); "vigor, strength" (mid-14c.); "love; a love affair" (c. 1300, hence in jollity "by fornication, out of wedlock"); "gallantry" (1530s); "state of splendor" (1540s).